1. Field of the Invention
The present invention relates to semi-reflective glass sheets, having metallic coatings deposited thereon, in which the transmission and reflection spectra are modified in both the visible and infrared spectra by controlling the amount and composition of the metal oxide compounds utilized in forming the protective layer of said coating.
2. Prior Art
It is well known that semi-reflective glass sheets can be constructed utilizing various metallic compounds coatings as protective layers which are deposited onto a reflective layer. Such coatings will impart heat-protective properties to a substrate material by substantially increasing the amount of infrared radiation reflected from the coated surface while maintaining a satisfactory radiation transmission coefficient in the visible range of the solar spectrum. Glazings of this type are often used in buildings to alleviate excessive heat during the summer months.
These prior art glazings are composed of three successive layers deposited on the surface of a glass substrate. The first, or anchoring, layer is deposited directly on the surface of the glass substrate. This layer is often a dielectric material or a metallic alloy, such as one containing nickel and chrome. The second layer, which provides the reflective properties, generally consists of a precious, semiprecious, or ordinary metal such as gold, silver, or copper, respectively. Various metallic alloys can also be employed to form this layer. The third, or protective, layer generally consists of a dielectric material such as zinc sulfide. This layer not only enhances the optical qualities of the entire coating but can also protect the reflective layer from the hazards which accompany exposure to the environment. These three layers can be deposited by various processes, such as thermal evaporation under vacuum.
The present invention is directed to a glass sheet in which the transmission and reflection spectra are controlled in both the visible and infrared spectra. More particularly, the glass sheets disclosed in this invention possess excellent transparency in the visible spectrum and high reflection in the thermal infrared spectrum, thereby reducing energy losses.